class_docstr: Keeps track of a running mean for seen states.
  
  The filter will be used to normalize observations and will be 
  online updated according to the seen observations of all actors.
code: def __repr__(self):
      return "MeanStdFilter({}, {}, {}, {}, {}, {})".format(
          self.shape,
          self.demean,
          self.destd,
          self.clip,
          self.rs,
          self.buffer,
      )
  
imports: import numpy
label_desc: Use image node_id 8 for calling the MeanStdFilter obj's underlying member method code with example usage: obj.__repr__() and returns: str